-AT_COMPILE_CXX([parser], [[x[1-8].o main.cc]])
-AT_CHECK([./parser], [0], [[expout]])
+# Check there is no 'yy' left.
+# C++ output relies on namespaces and still uses yy a lot.
+#
+# Check there is no 'YY' left.
+# Ignore comments, YYPUSH_MORE(_DEFINED)? (constant definition),
+# YY_\w+_INCLUDED (header guards).
+#
+# YYDEBUG (not renamed) can be read, but not changed.
+AT_CHECK([[$PERL -n -0777 -e '
+ s{/\*.*?\*/}{}gs;
+ s{//.*}{}g;
+ s{\b(YYPUSH_MORE(_DEFINED)?
+ |YY_\w+_INCLUDED
+ |YY_NULL
+ |(defined|if)\ YYDEBUG
+ )\b}{}gx;
+ while (/^(.*YY.*)$/gm)
+ {
+ print "$ARGV: $1\n";
+ }
+ if ($ARGV =~ /\.h$/)
+ {
+ while (/^(.*yy.*)$/gm)
+ {
+ print "$ARGV: $1\n";
+ }
+ }
+' -- *.hh *.h]])
+
+# Check that the headers are self-contained, and protected against
+# multiple inclusions. While at it, check they are sane for C++.
+for h in *.h *.hh
+do
+ # No shell expansion with AT_DATA.
+ cat >$h.cc <<EOF
+AT_DATA_SOURCE_PROLOGUE
+#include "$h"
+#include "$h"
+EOF
+ AT_COMPILE_CXX([$h.o])
+done
+
+# Do this late, so that other checks have been performed.
+AT_SKIP_IF_CANNOT_LINK_C_AND_CXX
+
+AT_COMPILE_CXX([parser], [[x[1-8].o -DCC_IS_CXX=$CC_IS_CXX main.cc]])
+AT_PARSER_CHECK([./parser], [0], [[expout]])